In the field of atomic energy, it is desirable to provide a system for sampling gas containing a mixed species of airborne solid and gaseous radioiodine for readout and assessment of the radioemissions from the collected iodine. This is particularly advantageous for iodine containing particulates and active vapors, such as hypoiodous acid, organic iodines and aerosols created by the accidental release of solid and gaseous products from nuclear reactors and the like, when the release contains gamma ray producing .sup.131 I and .sup.135 I, which have half-lives of about eight days and 6.7 hours respectively, since these radioisotopes of iodine and others can be absorbed and concentrated in the human thyroid gland.
One system that has been employed heretofore has separately collected the solid and gaseous species, and analyzed them with the aid of a multi-channel pulse height analyzer. However, this system, while reliable, has been difficult, complicated and expensive to operate, and has required trained personnel. Also, it has not been portable. It is further advantageous to provide a means and method for selectively and quickly determining the thyroid dose rate from airborne radioiodine with a conventional probe-type Geiger-Mueller detector, and to reduce the response of such a detection system to noble gas fission gases.